The present invention is concerned with the removal of contaminants from a gaseous medium, and more particularly with an apparatus and method employing char to adsorb alkali fumes and other very finely divided particulate material from a gasifier make-gas.
The term "adsorb" conventionally implies chemical attachment of molecules to a surface without their penetration beneath that surface so as to accumulate in the bulk of the material that is the adsorbent. The meaning of the term "adsorb" as used to describe the present invention is broadened to imply attachment of very fine particles to the surface of larger particles by any one of a number of mechanisms such as Van der Waal forces, electrostatic attraction, surface tension, etc.
An object of this invention is to provide a means for recycling char so as to increase the mass-flow ratio of char to gas. Another object is to provide a means for introducing char into the gas stream wherein the char is moving at substantially zero velocity as compared to the gas stream. A further object is to provide a means for removing alkali fumes, formed of minute particles, e.g. 3 microns or less, from a high temperature gas stream without having to cool the gas stream. Yet another object is to provide a means for separating char from the gas stream after the char has adsorbed the alkaki fumes in the gas stream.